Detecting device

ABSTRACT

A detecting device including a pressure sensor that is deformed by a load from an outside and causes stress dispersion includes a slip detecting unit that calculates a pressure center position using a pressure value detected by the pressure sensor, calculates a movement value of the calculated pressure center position using a temporal change of the pressure center position, and detects a slip on the basis of the calculated movement value of the pressure center position. The pressure sensor has a multilayer structure in which two detecting units that detect pressure are arranged to hold a viscoelastic body made of a viscoelastic material that is deformed by a load from the outside.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese PatentApplication JP 2007-199221 filed in the Japanese Patent Office on Jul.31, 2007, the entire contents of which being incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a detecting device, and, moreparticularly to a detecting device adapted to be capable of acquiringinformation on a slip necessary for stable gripping, skillfulmanipulation, and the like of an object by a robot hand.

2. Description of the Related Art

General tactile sensors in the past are classified into five typesdescribed below.

1. Examples of a sensor for contact (presence or absence of contact andconfirmation of approach) include a limit switch, a pressure sensor, anoptical sensor, a Hall element, and a capacitance sensor.

2. Examples of a sensor for a sense of pressure (pressure, a force, anda gripping force) include a semiconductor pressure sensor, a straingauge, a motor potential sensor, and a spring displacement sensor.

3. Examples of a sensor for distributed tactile senses (a pressuredistribution and a force distribution) include a pressure sensitiverubber+an electrode film, a pressure sensitive polymeric film+anelectrode plate, an optical sensor+a rubber plate, and an integratedsemiconductor pressure sensor.

4. Examples of a sensor for a sense of slip (relative displacement, sliposcillation, and a shearing force) include a roller or a ball+anencoder, an oscillation sensor, and a three-dimensional tactile sensor.

5. Examples of a sensor for a sense of force (a force and a moment)include a strain gauge+a structure, a strain block, an optical sensor+aspring, and a driving force sensor.

To perform complicated control such as stable gripping and skillfulmanipulation of an object by a robot hand, it is necessary to acquiregripping states such as a slip between the gripped object and fingers.

A tactile sensor for acquiring a gripping state among the tactilesensors described above, for example, JP-A-2006-47145 discloses a sensorhaving a multilayer structure in which a distributed pressure sensor anda flexible viscoelastic body are combined.

JP-A-2006-10407 discloses a detection sensor that includes a pressuresensitive element and a piezoelectric element and realizes detection ofa sense of slip by performing a waveform analysis of the piezoelectricelement and detection of a sense of force using the pressure sensitiveelement.

Moreover, JP-A-2004-226380 discloses a tactile sensor in whichrespective contact terminals of an element for detecting the pressure inthe vertical direction and an element for detecting the pressure in ashearing direction are arranged not to overlap each other on a sensorsurface and that obtains a sense of slip on the basis of a shearingforce and a vertical force detected from the elements.

SUMMARY OF THE INVENTION

However, the sensor disclosed in JP-A-2006-47145 measures a shape or adynamic characteristic of a pressed object (elasticity andviscoelasticity of an object) and does not measure a sense of slip. Thesensor disclosed in JP-A-2006-10407 detects oscillation due to a stickslip. Therefore, even if a slip itself can be detected, it is difficultto detect a direction of the slip.

The sensor disclosed in JP-A-2004-226380 obtains a sense of slip.However, this sense of slip is a sense of slip based on stick sliposcillation due to friction with an object, which is obtained by usingthe pressure in a shearing direction. In other words, when a signal ofthe pressure in the shearing direction is generated in a certainfrequency range, the sensor obtains the pressure as a sense of slip.

As described above, the various kinds of tactile sensors are present inthe related-art. However, as a sensor that acquires a slip between agripped object and fingers necessary for performing complicated controlsuch as stable gripping and skillful manipulation of an object by arobot hand, relatively few sensors are found other than the sensordisclosed in JP-A-2004-226380 that acquires a sense of slip based onstick slip oscillation due to friction with an object.

Therefore, besides the sensor, a proposal for more surely acquiringinformation on a slip necessary for stable gripping, skillfulmanipulation, and the like of an object by a robot hand is immediatelynecessary.

Therefore, it is desirable to make it possible to more surely acquireinformation on a slip necessary for stable gripping, skillfulmanipulation, and the like of an object by a robot hand.

According to an embodiment of the present invention, there is provided adetecting device including a pressure sensor that is deformed by a loadfrom the outside and causes stress dispersion. The detecting deviceincludes slip detecting means for calculating a pressure center positionusing a pressure value detected by the pressure sensor, calculating amovement value of the calculated pressure center position using atemporal change of the pressure center position, and detecting a slip onthe basis of the calculated movement value of the pressure centerposition. The pressure sensor has a multilayer structure in which twodetecting units that detect pressure are arranged to hold a viscoelasticbody made of a viscoelastic material that is deformed by a load from theoutside.

The slip detecting means can calculate a pressure center position from apressure distribution generated in the viscoelastic body by stressdispersion detected by a first one of the detecting units, calculate apressure center position from a pressure distribution generated in theviscoelastic body by stress dispersion detected by a second one of thedetecting units, and calculate a difference between the pressure centerpositions.

The slip detecting means can detect the slip on the basis of thecalculated difference.

The slip detecting means can detect, on the basis of the calculateddifference, a shearing force applied to the pressure sensor.

The slip detecting means can calculate, from a pressure distributiongenerated in the viscoelastic body by stress dispersion detected by afirst one of the detecting units and a pressure distribution generatedin the viscoelastic body by stress dispersion detected by a second oneof the detecting units, a difference between propagation speed ofpressure detected by the first detecting unit and propagation speed ofpressure detected by the second detecting unit.

The slip detecting means can detect the slip on the basis of thecalculated difference.

The slip detecting means can judge whether a movement value of thecalculated pressure center position is equal to or larger than apredetermined threshold and, when it is judged that the movement valueof the pressure center position is equal to or larger than thepredetermined threshold, detect the slip.

The slip detecting means can judge whether a sum of movement values ofthe calculated pressure center position is equal to or larger than apredetermined threshold and, when it is judged that the sum of themovement values of the pressure center position is equal to or largerthan the predetermined threshold, detect the slip.

The slip detecting means can multiply the movement values of thecalculated pressure center position with coefficients corresponding tolevels of the movement values of the pressure center position tocalculate a sum of the movement values of the pressure center position.

The slip detecting means can calculate a difference of a movementaverage value of the calculated pressure center position to calculate amovement value of the pressure center position.

The slip detecting means can calculate a difference of the calculatedpressure center position to calculate a movement value of the pressurecenter position.

The pressure sensor includes plural elements. The slip detecting meanscan detect, using a pressure value detected by the pressure sensor, anelement that performs detection of contact of an object with thepressure sensor and calculate a movement value of the pressure centerposition using a pressure value from the detected element.

The pressure sensor can have a viscoelastic body made of a viscoelasticmaterial on a surface thereof.

The viscoelastic body can be integrated with thin-film silicon rubber bya two-color molding method.

The viscoelastic body can be molded with an electrostatic shieldmaterial mixed therein.

The viscoelastic body and the pressure sensor can be integrated withthin-film silicon rubber by a two-color molding method.

A detecting device according to an embodiment of the present inventionis a detecting device including a pressure sensor that is deformed by aload from the outside and causes stress dispersion. In the detectingdevice, a pressure center position is calculated by using a pressurevalue detected by the pressure sensor, a movement value of the pressurecenter position is calculated by using a temporal change of thecalculated pressure center position, a slip is detected on the basis ofthe calculated movement value of the pressure center position, and thepressure sensor has a multilayer structure in which two detecting unitsthat detect pressure are arranged to hold a viscoelastic body made of aviscoelastic material that is deformed by a load from the outside.

According to the present invention, it is possible to more surelyacquire information on a slip necessary for stable gripping, skillfulmanipulation, and the like of an object by a robot hand.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an example of the external structure of arobot hand manipulator according to an embodiment of the presentinvention;

FIG. 2 is a perspective view showing an example of the externalstructure of a sensor shown in FIG. 1;

FIG. 3 is a diagram showing an example of the internal structure of thesensor shown in FIG. 2;

FIG. 4 is a graph showing an example of compression and tensioncharacteristics of a viscoelastic material;

FIG. 5 is a diagram showing an example of the structure of acapacitance-type pressure sensor configuring a pressure detecting unitshown in FIG. 2;

FIG. 6 is a block diagram showing an example of the internal electricstructure of the robot hand manipulator;

FIG. 7 is a block diagram showing an example of the structure of asignal processing unit shown in FIG. 6;

FIG. 8 is a diagram showing an example of shapes of an input sectionbefore loading and after loading;

FIG. 9 is a diagram showing a graph of a pressure value and time and agraph of a pressure value and a position in the case of FIG. 8;

FIG. 10 is a diagram showing an example of shapes of the input sectionbefore shifting and after shifting;

FIG. 11 is a diagram showing graphs of a pressure value and a positionin the case of FIG. 10;

FIG. 12 is a diagram showing a graph of a center pressure position andtime;

FIG. 13 is a diagram showing models of a pure shearing stress state;

FIG. 14 is a diagram showing another example of the external structureof the sensor shown in FIG. 2;

FIG. 15 is a diagram showing another example of a material of the inputsection shown in FIG. 2; and

FIG. 16 is a block diagram showing an example of the structure of apersonal computer to which the present invention is applied.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be hereinafter explained. Acorrespondence relation between elements of the present invention andthe embodiments described or shown in the specification or the drawingsis described as follows. This description is a description forconfirming that the embodiments supporting the present invention aredescribed or shown in the specification or the drawings. Therefore, evenif there is an embodiment that is described or shown in thespecification or the drawings but is not described herein as anembodiment corresponding to an element of the present invention, thisdoes not means that the embodiment does not correspond to the element.Conversely, even if an embodiment is described herein as an embodimentcorresponding to an element of the present invention, this does notmeans that the embodiment does not correspond to elements other than theelement.

A detecting device according to an embodiment of the present inventionis a detecting device including a pressure sensor (e.g., a sensor 21shown in FIG. 3) that is deformed by a load from the outside and causesstress dispersion. The detecting device includes slip detecting means(e.g., a signal processing unit 53 shown in FIG. 6) for calculating apressure center position using a pressure value detected by the pressuresensor, calculating a movement value of the calculated pressure centerposition using a temporal change of the pressure center position, anddetecting a slip on the basis of the calculated movement value of thepressure center position. The pressure sensor has a multilayer structurein which two detecting units (e.g., pressure detecting units 42-1 and42-2 shown in FIG. 3) that detect pressure are arranged to hold aviscoelastic body (e.g., a deforming section 41 shown in FIG. 3) made ofa viscoelastic material that is deformed by a load from the outside.

The slip detecting means can calculate a pressure center position from apressure distribution generated in the viscoelastic body by stressdispersion detected by a first one of the detecting units, calculate apressure center position from a pressure distribution generated in theviscoelastic body by stress dispersion detected by a second one of thedetecting units, and calculate a difference (e.g., a distance “d” shownin FIG. 13) between the pressure center positions.

An embodiment of the present invention is explained below with referenceto the accompanying drawings.

FIG. 1 shows an example of the external structure of a robot handmanipulator according to the embodiment of the present invention.

As shown on the left side in FIG. 1, the robot hand manipulator includesa robot hand 1 and a supporting unit 2 that supports the robot hand 1.

The robot hand 1 includes a shoulder joint section 11-1, an upper armsection 11-2, an elbow joint section 11-3, a forearm section 11-4, awrist section 11-5, and a hand section 11-6 that are actually-operatingsections (these sections are generally referred to as joint section 11when it is unnecessary to distinguish the sections from one another).

Sensors 21-1 and 21-2 are provided in the upper arm section 11-2 and theforearm section 11-4 of the robot hand 1, respectively. As shown on theright side in FIG. 1 in enlargement, sensors 21-3 and 21-4 are providedin a palm configuring the hand section 11-6 of the robot hand 1. Asensor 21-5 is provided above a first joint on a finger palm surface ofa thumb forming the hand section 11-6. A sensor 21-6 is provided betweenthe first joint and a second joint on the finger palm surface of thethumb. A sensor 21-7 is provided above a first joint on a finger palmsurface of an index finger. A sensor 21-8 is provided between the firstjoint and a second joint on the finger palm surface of the index finger.A sensor 21-9 is provided between the second joint and a third joint onthe finger palm surface of the index finger.

A sensor 21-10 is provided above a first joint on a finger palm surfaceof a middle finger. A sensor 21-11 is provided between the first jointand a second joint on the finger palm surface of the middle finger. Asensor 21-12 is provided between the second joint and a third joint onthe finger palm surface of the middle finger. A sensor 21-13 is providedabove a first joint on a finger palm surface of a third finger. A sensor21-14 is provided between the first joint and a second joint on thefinger palm surface of the third finger. A sensor 21-15 is providedbetween the second joint and a third joint on the finger palm surface ofthe third finger. A sensor 21-16 is provided above a first joint on afinger palm surface of a little finger. A sensor 21-17 is providedbetween the first joint and a second joint on the finger palm surface ofthe little finger. A sensor 21-18 is provided between the second jointand a third joint on the finger palm surface of the little finger.

The sensors 21-1 to 21-18 provided in the robot hand 1 (the sensors arehereinafter simply referred to as sensor 21 when it is unnecessary tospecifically distinguish the sensors from one another; the same appliesin other cases) include capacitance-type pressure sensors that detectonly a normal force (e.g., pressure) perpendicular to surfaces of thesensors. The sensor 21 has on the surface thereof a viscoelastic bodyhaving softness like the human skin. The viscoelastic body is deformedinto various shapes by a force received from the outside and a form ofthe force, whereby pressure is dispersed to the sensor 21 on the inside.

The sensor 21 detects, when an object comes into contact with theviscoelastic body, a dispersed pressure value of the object (hereinafteralso referred to as distributed pressure value). The sensor 21 detects,on the basis of the detected distributed pressure value, a slip betweena gripped object and fingertips, which is gripping information necessaryfor performing complicated control such as stable gripping and skillfulmanipulation of an object by the robot hand 1.

The “slip” in gripping and manipulation in this embodiment is defined asdescribed below.

In general, a relative motion between fingers and an object is called a“slip”. The relative motion is roughly divided into a “translationalmotion” and a “rotational motion”. The “translational motion” is amotion in a direction orthogonal to a gripping force (a normal force) ata gripping contact point (a shearing direction or a tangent direction).The “rotational motion” is a “rolling motion” of the object rotationallymoving while keeping contact with the fingers and a “rotational motionaround a normal axis” at the gripping contact point. These motions aredistinguished from each other by being referred to as a translationalslip and a rotational slip. However, these motions often occursimultaneously in combination.

On the other hand, when stability, robustness, and the like of grippingare taken into account, fingertips desirably have the flexiblestructure. When an object is gripped by the flexible fingertips, ashearing force is applied to the object. Then, a relative motiongradually occurs from an outer peripheral portion of a contact area andan “initial local slip” in a mixed area of a fixed area and a slippingarea occurs. When the shearing force is further applied, after a certainpoint, the fingertips and the object reach a motion state (a “slip” in anarrow sense) dominated by a coefficient of dynamic friction. At thetime of this “initial local slip” equivalent to the start of a slip,since oscillation occurs, it is possible to observe the initial localslip. At a stage before reaching the initial local slip, the contactarea of the fingertips and the object is generally unchanged. However,there is also a state in which a flexible material is deformed to cause“shift”.

If the gripping and the manipulation are controlled on the basis of onlya complete relative motion between the fingers and the object, thegripping and the manipulation is often not satisfactorily be realizedbecause of a delay in the control. Therefore, considering that it isalso important to predict a “slip” and prevent the slip, a slipincluding the “initial local slip” and the “shift” is referred to a“slip” in a broad sense.

The sensor 21 shown in FIG. 1 can detect the “translational motion” andthe “rotational motion” including the “initial local slip” and the“shift” in the “slip” defined in this way.

The robot hand manipulator actuates actuators of the respective jointsections making use of softness of the sensor 21 itself, grippabilitydue to friction of the surface, and the like on the basis of a detectedslip between a gripped object and the fingertips to thereby grip a mugand move or carry the mug.

As described above, the robot hand manipulator can skillfully grip andmanipulate arbitrary objects having various sizes, shapes, surfacestates, weights, and the like.

FIG. 2 is a perspective view showing an example of the externalstructure of the sensor 21.

The sensor 21 roughly includes an input section 31 that is a sectiontouched by an object and made of a deformable material, a fixing section32 that supports the input section 31, and an external connectionsection 33 through which power is inputted and a detection result of thesensor 21 is outputted to, for example, a main control unit 101 (FIG. 6described later) of the robot hand manipulator.

In the example in FIG. 2, in the input section 31, an input surface 31 ais formed in a square pole shape. In the following explanation, asurface parallel to the input surface 31 a is an xy plane of an xyzcoordinate system and a direction perpendicular to the input surface 31a is a z axis direction unless specifically noted otherwise.

FIG. 3 shows the internal structure of the sensor 21 shown in FIG. 2. Inthe upper part in the figure, a plan view of the sensor 21 viewed fromabove is shown. In the lower part in the figure, a side sectional viewof the sensor 21 is shown.

The input section 31 roughly includes a deforming section 41 and twopressure detecting units 42-1 and 42-2 (these pressure detecting unitsare referred to as pressure detecting unit 42 when it is unnecessary todistinguish the same from one another). The input section 31 includes athree-layer structure in which the pressure detecting unit 42-1 is a toplayer, the deforming section 41 is a middle layer, and the pressuredetecting unit 42-2 is a bottom layer. In other words, the input section31 has a multilayer structure in which the pressure detecting unit 42-1and the pressure detecting unit 42-2 are arranged to hold the deformingsection 41. On an upper side in FIG. 3, the input section 31, thepressure detecting unit 42-1, and the deforming section 41 are shown ina state in which the sections are made transparent stepwise to show theinternal structure thereof.

The deforming section 41 is made of a viscoelastic material (aviscoelastic body) having a viscoelastic characteristic such as asilicon gel material. The deforming section 41 can be easily deformed bya load from the outside.

As the viscoelastic material, silicon gel having high heat resistance,low temperature resistance, slidability, and abrasion resistance issuitable. However, other materials can also be used.

A boundary between the input section 31 and the fixing section 32 isformed as a binding surface. The input section 31 and the fixing section32 are fixed by bonding or integral molding. Therefore, because ofincompressibility equivalent to that of a rubber material and the like,for example, a so-called bulging phenomenon in which a part of the sidesand the upper surface expands is caused. It is recognized as a result ofthe experiment by the applicant that a form of the bulging phenomenonshows various characteristics according to a load value and an inputsurface shape.

FIG. 4 is a graph showing an example of compression and tensioncharacteristics of the viscoelastic material used in the deformingsection 41.

The ordinate represents a stress [Mpa] generated against a load (anexternal force) acting on the viscoelastic material. The abscissarepresents distortion (%), which is a degree of deformation due to theload on the material with respect to an original state.

In this example, when a load of compression is applied in a state inwhich distortion does not occur (i.e., distortion is 0%), the distortionchanges to about −90 and the stress increases little by little in aminus direction (downward in the figure) until the distortion reachesabout −50. When the distortion exceeds about −60, the stress suddenlyincreases.

On the other hand, when a load of tension is applied when the distortionis 0, the distortion changes to 400% and, during the change, the stressgently increases in a plus direction (upward in the figure) comparedwith the increase in the stress in the case of compression. In the caseof this example, distortion equal to or larger than 400% is notmeasured. However, it is considered that the distortion changes to acertain degree exceeding 400% and the stress increases in the samemanner.

Referring back to FIG. 3, the pressure detecting unit 42 includes, forexample, a capacitance-type pressure sensor that detects pressure usinga capacitance change.

Stress relaxation and stress dispersion are caused by the deformation ofthe deforming section 41 and pressure is dispersed to the pressuredetecting unit 42 on the inside. Therefore, the pressure detecting unit42 can obtain sensing performance equal to or higher than spatialresolution of the capacitance-type pressure sensor on the basis of aninterpolation characteristic due to the deformation of the viscoelasticbody.

FIG. 5 shows details of the pressure detecting unit 42-1 shown in FIG.3.

The pressure detecting unit 42-1 includes, for example, plural pressuredetection elements (hereinafter also referred to as sensor elements)52-1 arranged in a matrix shape on a flexible substrate 51-1. In otherwords, a sensor configured by the pressure detecting unit 42-1 is acapacitance-type pressure sensor and is also called a distributedpressure sensor. In an example in FIG. 5, for convenience ofexplanation, one sensor element is denoted by a reference numeral andreference numerals of the other sensor elements are omitted.

In the case of the example in FIG. 5, the pressure detecting unit 42-1includes one-hundred sixty-eight sensor elements 52-1 arranged invertical 21 columns×horizontal 8 rows. Lead-out lines are inputted to asignal processing unit 53-1 from the respective columns and therespective rows of the sensor elements 52-1. Distributed pressure valuesdetected by the respective sensor elements 52-1 are inputted to thesignal processing unit 53-1 via the lead-out lines and subjected topredetermined signal processing by the signal processing unit 53-1. Aresult of the signal processing is outputted to the outside of thesensor 21.

The pressure detecting unit 42-1 is configured as described above. Thepressure detecting unit 42-1 is explained above. Since the pressuredetecting unit 42-2 is basically configured the same as the pressuredetecting unit 42-1, illustration and explanation of the pressuredetecting unit 42-2 are omitted. A flexible substrate, a sensor element,and a signal processing unit in the pressure detecting unit 42-2corresponding to the flexible substrate 51-1, the sensor element 52-1,and the signal processing unit 53-1 in the pressure detecting unit 42-1are referred to as flexible substrate 51-2, sensor element 52-2, andsignal processing unit 53-2, respectively.

The pressure detecting unit 42-1 and the pressure detecting unit 42-2are configured as described above. Therefore, precisely, the sensor 21is configured by arranging, in a three-layer structure, the flexiblesubstrate 51-1 on which the pressure detecting unit 42-1 and the signalprocessing unit 53-1 are arranged, the deforming section 41, and theflexible substrate 51-2 on which the pressure detecting unit 42-2 andthe signal processing unit 53-2 are arranged.

FIG. 6 shows an example of the electric structure of the robot handmanipulator shown in FIG. 1.

In the example in FIG. 6, the robot hand manipulator includes a maincontrol unit 101, actuators 102-1, 102-2, and the like, and sensors21-1, 21-2, and the like.

The sensors 21 arranged in predetermined positions corresponding topredetermined joint sections 11 as shown in FIG. 1 electrically includethe pressure detecting units 42-1, the signal processing units 53-1, thepressure detecting units 42-2, and the signal processing units 53-2 asexplained with reference to FIG. 5.

The pressure detecting units 42-1 at the top layers of the sensors 21output distributed pressure values, which are detected by the pluralsensor elements 52-1 using a capacitance change as a detectionprinciple, to the signal processing units 53-1. The pressure detectingunits 42-2 at the bottom layer of the sensors 21 output distributedpressure values, which are detected by the plural sensor elements 52-2using a capacitance change as a detection principle, to the signalprocessing units 53-2. The detection principle for a distributedpressure value may be other than the capacitance change. For example,the detection principle may be a resistance value change or, if adistributed pressure value can be obtained, a sensor configured bysimply arranging pressure sensitive rubber may be used.

The signal processing units 53-1 and the signal processing units 53-2 ofthe sensors 21 perform predetermined kinds of signal processing(described later), respectively, using the distributed pressure valuesfrom the pressure detecting units 42-1 and the pressure detecting units42-2 to thereby detect a slip between a gripped object and thefingertips and output information on the detected slip to the maincontrol unit 101 on a real time basis.

The main control unit 101 incorporates a CPU (Central Processing Unit),a memory, and the like. Control programs stored in the memory areexecuted by the CPU, whereby the main control unit 101 performs variouskinds of processing.

For example, the main control unit 101 receives the information on theslip between the gripped object and the fingertips detected by thesensors 21. The main control unit 101 controls necessary ones among theactuators 102 using softness of the sensors 21 themselves, grippabilityby friction of the surfaces, and the like on the basis of information ona slip between the gripped object and the fingertips from the sensors 21to drive the predetermined joint sections 11, cause the robot hand 1 togrip the object and, for example, move or carry the object.

The actuators 102 are incorporated in the predetermined joint sections11 (i.e., the shoulder joint section 11-1, the elbow joint section 11-3,the wrist section 11-5, and the hand section 11-6) of the robot hand 1,respectively, and drive the predetermined joint sections 11 according toa driving signal from the main control unit 101. Consequently, thepredetermined joint sections 11 can rotate with predetermined degrees offreedom.

FIG. 7 shows an example of the electric structure of the signalprocessing unit 53-1 of the sensor 21. Information on a distributedpressure value from the pressure detecting unit 42-1 is inputted to acontact detecting section 121 and a pressure-center calculating section122 of the signal processing unit 53-1.

The contact detecting section 121 performs contact detection in thesensor elements 52-1 using the distributed pressure value from thepressure detecting unit 42-1 and outputs information on the sensorelements 52-1, in which detection of contact of an object with thesensor 21 (the deforming section 41) is performed, to thepressure-center calculating section 122.

For example, it is assumed that, when the pressure detecting unit 42-1includes m×n (in the case of the example in FIG. 5, considering that thelength is the horizontal direction, m=21 and n=8) sensor elements 52-1;m (x=0, 1, 2, . . . , m−1) in the horizontal direction (x) and n (y=0,1, 2, . . . , n−1) in the vertical direction (y). When outputs (i.e.,pressure values) P(x, y) of the respective sensor elements 52-1 exceed acertain threshold th(x, y), i.e., the following formula (1) issatisfied, the contact detecting section 121 judges that the sensorelements 52-1 detect contact of the object with the input section 31(the deforming section 41). The threshold th(x, y) may be the same forall the sensor elements 52-1.P(x,y)>th(x,y)   (1)

When a sum of outputs P(x, y) of the respective sensor elements 52-1exceeds a certain threshold th, i.e., when the following formula (2) issatisfied, the contact detecting section 121 may judge that the sensorelements 52 detect contact.

$\begin{matrix}{{\sum\limits_{y = 0}^{n - 1}\;{\sum\limits_{x = 0}^{m - 1}\;{P\left( {x,y} \right)}}} > {th}} & (2)\end{matrix}$

The pressure-center calculating section 122 calculates a pressure centerposition using the distributed pressure value from the pressuredetecting unit 42-1 and supplies the pressure center position to apressure-center-movement calculating section 123.

Specifically, when pressure values detected by the sensor elements 52-1of the pressure detecting unit 42-1 is represented as P(x, y) and unitareas of the respective sensor elements 52-1 are represented as S(x, y),pressure center positions COPx and COPy are calculated by the followingformula (3):

$\begin{matrix}{{{COPx} = \frac{\sum\limits_{y = 0}^{n - 1}\;{\sum\limits_{x = 0}^{m - 1}\;{{P\left( {x,y} \right)} \times {S\left( {x,y} \right)} \times x}}}{\sum\limits_{y = 0}^{n - 1}\;{\sum\limits_{x = 0}^{m - 1}\;{{P\left( {x,y} \right)} \times {S\left( {x,y} \right)}}}}}{{COPy} = {\frac{\sum\limits_{y = 0}^{n - 1}\;{\sum\limits_{x = 0}^{m - 1}\;{{P\left( {x,y} \right)} \times {S\left( {x,y} \right)} \times y}}}{\sum\limits_{y = 0}^{n - 1}\;{\sum\limits_{x = 0}^{m - 1}\;{{P\left( {x,y} \right)} \times {S\left( {x,y} \right)}}}}.}}} & (3)\end{matrix}$

A denominator on the right side of formula (3) is a sum of forcesapplied in a tangent direction and a numerator on the right side is asum of torques. Therefore, according to formula (3), a pressure centerposition is calculated as a representative point of positions to whichthe torques are applied.

As in the case of the example in FIG. 5, when all the unit areas S(x, y)of the sensor elements 52-1 are the same, the pressure center positionsCOPx and COPy can be simply calculated by the following formula (4):

$\begin{matrix}{{{COPx} = \frac{\sum\limits_{y = 0}^{n - 1}\;{\sum\limits_{x = 0}^{m - 1}\;{{P\left( {x,y} \right)} \times x}}}{\sum\limits_{y = 0}^{n - 1}\;{\sum\limits_{x = 0}^{m - 1}\;{P\left( {x,y} \right)}}}}{{COPy} = {\frac{\sum\limits_{y = 0}^{n - 1}\;{\sum\limits_{x = 0}^{m - 1}\;{{P\left( {x,y} \right)} \times y}}}{\sum\limits_{y = 0}^{n - 1}\;{\sum\limits_{x = 0}^{m - 1}\;{P\left( {x,y} \right)}}}.}}} & (4)\end{matrix}$

In formula (3) and formula (4), the pressure values P(x, y) of all thesensor elements 52-1 are used. However, the pressure center positionsCOPx and COPy can also be calculated by using only the pressure valuesP(x, y) of the sensor elements that satisfy formula (1) or formula (2),i.e., detect contact. In this case, when contact is not detected, sincea pressure center position is not calculated, the calculation can bestopped.

In the case of the example in FIG. 5, the sensor elements 52-1 arearranged in the horizontal direction and the vertical direction,respectively. However, the sensor elements 52-1 can perform the sameprocessing when the sensor elements 52-1 are arranged only in thehorizontal direction or the vertical direction. When the sensor element52-1 is arranged only in the horizontal direction, n is 0 and only aresult of the pressure center position COPx is used. When the sensorelements 52-1 are arranged only in the vertical direction, m is 0 andonly a result of the pressure center position COPy is used.

The pressure center positions COPx and COPy calculated as describedabove take only values of 0≦COPx≦m−1 and 0≦COPy≦n−1 according to apressure value. Therefore, it is possible to use a detection result ofcontact position detection in the pressure-center-movement calculatingsection 123 by passing the pressure center positions COPx and COPy tothe pressure-center-movement calculating section 123.

The pressure-center-movement calculating section 123 accumulates, intime series, pressure center positions passed from the pressure-centercalculating section 122. The pressure-center-movement calculatingsection 123 calculates, for example, a difference of a moving averagevalue of the accumulated pressure center positions or a difference ofthe pressure center positions and outputs the calculated difference to aslip-sense detecting section 124.

For example, respective kinds of time series information of pressurecenter positions are represented as COPx(t) and COPy(t). In order toabsorb very small fluctuation, the pressure-center-movement calculatingsection 123 applies low-pass filtering or moving averaging to COPx(t)and COPy(t). In the following explanation, simpler moving averaging isused in a calculation. When fluctuation (noise) is small, low-passfiltering or moving averaging processing does not have to be performed.

When numbers to be moving averaged is represented as M, moving averagesCOPx_(MA)(t) and COPy_(MA)(t) are represented by the following formula(5) by using COPx(t) and COPy(t) accumulated in time series:

$\begin{matrix}{{{{COPx}_{MA}(t)} = {\frac{1}{M}{\sum\limits_{i = 0}^{M - 1}\;{{COPx}\left( {t - i} \right)}}}}{{{COPy}_{MA}(t)} = {\frac{1}{M}{\sum\limits_{i = 0}^{M - 1}\;{{{COPy}\left( {t - i} \right)}.}}}}} & (5)\end{matrix}$

The pressure-center-movement calculating section 123 accumulates thecalculated moving averages COPx_(MA)(t) and COPy_(MA)(t) in time seriesas well. The pressure-center-movement calculating section 123 calculatesa pressure center movement calculated value as indicated by thefollowing formula (6) using the accumulated moving average values.Dx(t,i)=COPx _(MA)(t)−COPx _(MA)(t−i)Dy(t,i)=COPy _(MA)(t)−COPy _(MA)(t−i)   (6)

In formula (6), for example, differences between a moving average valueat time t and moving average values at time t−1, time t−2, and time t−3are calculated. In other words, changes in time in plural number oftimes are calculated. Pressure center movement calculated values Dx(t,i) and Dy(t, i), which are the differences of the moving average values,are outputted to the slip-sense detecting section 124.

The slip-sense detecting section 124 performs, for example, a pressurecenter movement detecting calculation using a calculation result (i.e.,the pressure center movement calculated values) from thepressure-center-movement calculating section 123 and detects a slipaccording to a calculation result of the pressure center movementdetecting calculation. The slip-sense detecting section 124 also detectsa slip using the calculation result from the pressure-center-movementcalculating section 123. When the calculation result of the pressurecenter movement detecting calculation is used, the slip-sense detectingsection 124 multiplies the pressure center movement calculated valuewith coefficients corresponding to levels of the pressure centermovement calculated values to perform the pressure center movementdetecting calculation. The slip-sense detecting section 124 detects aslip according to a calculation result of the pressure center movementdetecting calculation.

In other words, the slip-sense detecting section 124 judges whether thecalculation result of the pressure center movement detecting calculationor the calculation result from the pressure-center-movement calculatingsection 123 exceeds a predetermined threshold (hereinafter referred toas threshold for judgment) and, when it is judged that the calculationresult exceeds the threshold for judgment, detects a slip.

For example, the slip-sense detecting section 124 performs a calculationof formula (7) using the pressure center movement calculated valuesDx(t, i) and Dy(t, i) from the pressure-center-movement calculatingsection 123 and calculates movement detection coefficients Kx(i) andKy(i).

$\begin{matrix}{{{Kx}(i)} = \left\{ {{\begin{matrix}{Cs} & {{\text{:}{{{Dx}\left( {t,i} \right)}}} < {{threshold} \cdot i}} \\{C\; 1} & {{\text{:}{{{Dx}\left( {t,i} \right)}}} \geq {{threshold} \cdot i}}\end{matrix}{{Ky}(i)}} = \left\{ \begin{matrix}{Cs} & {{\text{:}{{{Dy}\left( {t,i} \right)}}} < {{threshold} \cdot i}} \\{C\; 1} & {{\text{:}{{{Dy}\left( {t,i} \right)}}} \geq {{threshold} \cdot i}}\end{matrix} \right.} \right.} & (7)\end{matrix}$where, threshold is a fixed value and Cs and Cl are constants having arelation 0<Cs<Cl. For example, Cs=1 and Cl=2 are used. Therefore,threshold·i is a value that increases as “i” increases. In other words,the movement detection coefficients Kx(i) and Ky(i) are coefficientsthat are calculated according to levels of the pressure center movementcalculated values Dx(t, i) and Dy(t, i). More specifically, the movementdetection coefficients Kx(i) and Ky(i) are coefficients that arecalculated according to a result of comparison of the levels of thepressure center movement calculated values Dx(t, i) and Dy(t, i) and thevalue that increases as time elapses. Note that threshold may be avariable value.

The slip-sense detecting section 124 performs a pressure center movementdetecting calculation using values calculated by formula (6) and formula(7). An arithmetic expression of the pressure center movement detectingcalculation is represented by formula (8).Mdx(t,i)=Kx(i)·Dx(t,i)Mdy(t,i)=Ky(i)·Dy(t,i)   (8)

Moreover, the slip-sense detecting section 124 performs a slip sensedetecting calculation using a value calculated by formula (8). Anarithmetic expression of the slip sense detecting calculation isrepresented by formula (9).

$\begin{matrix}{{{{Sdx}(t)} = {\sum\limits_{i = 1}^{N}\;{{Mdx}\left( {t,i} \right)}}}{{{Sdy}(t)} = {\sum\limits_{i = 1}^{N}\;{{Mdy}\left( {t,i} \right)}}}} & (9)\end{matrix}$

Slip sense detection values Sdx and Sdy calculated by formula (9) areamounts having a characteristic that the amounts increase as a slipamount increases and a direction component thereof is substantiallysaved. When the slip-sense detecting section 124 judges that the slipsense detection values Sdx and Sdy exceed the threshold for judgment,the slip-sense detecting section 124 detects a slip.

By setting a value of N in formula (9) large and setting threshold informula (7) small, it is possible to detect a slip even when an objectslips very slowly. By setting a value of N small and setting thresholdlarge, it is possible to detect only a slip when the object slips fast.Therefore, the slip-sense detecting section 124 can acquire plural kindsof slip sense detection values Sdx and Sdy by applying the calculationto plural N's and plural thresholds and can use the slip sense detectionvalues Sdx and Sdy properly according to a purpose of detection.

The slip detected by the slip-sense detecting section 124 as describedabove and a direction of the slip are outputted to the main control unit101 as information on the slip on a real time basis. Consequently, themain control unit 101 can accurately control an object grippingoperation of the robot hand 1.

The pressure center movement calculated values Dx(t, i) and Dy(t, i)described above are not only calculated by formula (6). For example,when fluctuation is small, the pressure center movement calculated valueDx(t, i) and Dy(t, i) can also be calculated by the following formula(10) by using COPx(t) and COPy(t) accumulated in time series.Dx(t,i)=COPx(t)−COPx(t−i)Dy(t,i)=COPy(t)−COPy(t−i)   (10)

The slip sense detection values Sdx and Sdy described above are not onlycalculated by formula (9). The slip sense detection values Sdx and Sdycan also be calculated as described below.

For example, when fluctuation is extremely small, the slip sensedetection values Sdx and Sdy are calculated by setting “i” of Dx(t, i)and Dy(t, i) to 1, respectively. In other words, the slip sensedetection values Sdx and Sdy are represented by the following formula(11):Sdx(t)=Mdx(t,1)=COPx(t)−COPx(t−1)Sdy(t)=Mdy(t,1)=COPy(t)−COPy(t−1)   (11)

In this case, a slow slip and a fast slip can be detected by comparingthe slip sense detection values Sdx and Sdy with plural thresholds forjudgment. For example, a slow slip can be detected by comparing the slipsense detection values Sdx and Sdy with a small threshold for judgmentand a high slip can be detected by comparing the slip sense detectionvalues Sdx and Sdy with a large threshold for judgment.

Moreover, when fluctuation is small but is not so small as describedabove, the slip sense detection values Sdx and Sdy can be calculated bysetting “i” of Dx(t, i) and Dy(t, i) to N, respectively. In this case,the slip sense detection values Sdx and Sdy are represented by thefollowing formula (12).Sdx(t)=Mdx(t,N)=COPx(t)−COPx(t−N)Sdy(t)=Mdy(t,N)=COPy(t)−COPy(t−N)   (12)

In this case, as in the above case, an extremely slow slip and anextremely fast slip can also be detected by comparing the slip sensedetection values Sdx and Sdy with plural N's and plural thresholds forjudgment. In other words, a slow slip can be detected by setting N'slarge and setting the thresholds for judgment small and a fast slip canbe detected by setting N's small and setting the thresholds for judgmentlarge.

The same holds true when a moving average of pressure center positionsis calculated. The slip sense detection values Sdx and Sdy at the timewhen the moving average is calculated can be calculated by setting “i”of Dx(t, i) and Dy(t, i) to 1, respectively, and can also be calculatedby setting “i” of Dx(t, i) and Dy(t, i) to N, respectively. In otherwords, the slip sense detection values Sdx and Sdy calculated by setting“i” of Dx(t, i) and Dy(t, i) at the time when the moving average iscalculated to 1 are represented by the following formula (13) and theslip sense detection values Sdx and Sdy calculated by setting “i” ofDx(t, i) and Dy(t, i) at the time when the moving average is calculatedto N are represented by the following formula (14):Sdx(t)=Mdx(t,1)=COPx _(MA)(t)−COPx _(MA)(t−1)Sdy(t)=Mdy(t,1)=COPy _(MA)(t)−COPy _(MA)(t−1)   (13)Sdx(t)=Mdx(t,N)=COPx _(MA)(t)−COPx _(MA)(t−N)Sdy(t)=Mdy(t,N)=COPy _(MA)(t)−COPy _(MA)(t−N)   (14)

In the former case (i.e., when the slip sense detection values Sdx andSdy are calculated by setting “i” of Dx(t, i) and Dy(t, i) at the timewhen the moving average is calculated to 1), as in the above case, aslow slip and a fast slip can be detected by comparing the slip sensedetection values Sdx and Sdy with plural thresholds for judgment. Forexample, a slow slip can be detected by comparing the slip sensedetection values Sdx and Sdy with a small threshold for judgment and afast slip can be detected by comparing the slip sense detection valuesSdx and Sdy with a large threshold for judgment.

In the latter case (i.e., when the slip sense detection values Sdx andSdy are calculated by setting “i” of Dx(t, i) and Dy(t, i) at the timewhen the moving average is calculated to N), as in the above case, anextremely slow slip and an extremely fast slip can be detected bycomparing the slip sense detection values Sdx and Sdy with plural N'sand plural thresholds for judgment. In other words, a slow slip can bedetected by setting N's large and setting the thresholds for judgmentsmall and a fast slip can be detected by setting N's small and settingthe thresholds for judgment large.

The signal processing unit 53-1 is configured as described above andcalculates a slip sense detection values from a pressure received by theupper layer portion of the sensor 21. The signal processing unit 53-2 isbasically configured the same as the signal processing unit 53-1.Therefore, illustration and explanation of the signal processing unit53-2 are omitted. However, the signal processing unit 53-2 calculates aslip sense detection value from a pressure received by the lower layerportion of the sensor 21.

Operations of the sensor 21 are explained below.

FIG. 8 shows an example of a shape of the input section 31 beforeloading (on an upper side of the figure) and an example of a shape ofthe input section 31 after loading (on a lower side of the figure). Inthe examples in FIG. 8, a left direction in the figure represents a plusdirection of an x axis of an xyz coordinate system and an upwarddirection in the figure represents a plus direction of a z axis of thexyz coordinate system.

A pressure tip A is depressed to a predetermined position (in theexample in FIG. 8, a position of a graduation 9) on the x axis of theinput section 31. A load Fz in a minus direction (a downward directionin the figure) of the z axis is applied to the position of the inputsection 31.

When the load Fz in the minus direction of the z axis is applied to theinput section 31 in this way, the deforming section 41 is graduallydeformed because the input section 31 and the fixing section 32 arefastened by bonding or integral molding, a boundary between the inputsection 31 and the fixing section 32 is formed as a binding surface, andthe deforming section 41 has incompressibility equivalent to that of arubber material. A pressure distribution occurs because of stressdispersion (synonymous with stress relaxation). After loading, aso-called bulging phenomenon in which a part of the sides and the uppersurface expands more than an original shape indicated by a dotted lineis caused. A pressure distribution in that state occurs.

When attention is paid to this pressure distribution, a pressure valuemeasured by the sensor element 52-1 located in a pressure centerposition C by the load Fz among the sensor elements 52-1 configuring thepressure detecting unit 42-1 gradually increases as indicated by a curve103 of a graph of a pressure value and time shown in FIG. 9 (a graph ina lower part of FIG. 9). When the pressure value reaches a predeterminedvalue, the pressure value comes into a statically determinate state inwhich the predetermined value is maintained.

A pressure value measured by the sensor element 52-2 located in apressure center position D by the load Fz among the sensor elements 52-2configuring the pressure detecting units 42-2 also gradually increasesas indicated by a curve 104 of the graph of a pressure value and timeshown in FIG. 9 (the graph in the lower part of FIG. 9). When thepressure value reaches a predetermine value, the pressure value comesinto a statically determinate state in which the predetermined value ismaintained.

A distribution of pressure values in the pressure detecting unit 42-1 inthe statically determinate state has a substantially symmetrical curvedshape with the pressure value in the pressure center position C (aroundthe graduation 9) set as the maximum and pressure values at both ends ofa distribution range of the pressure values set as the minimum asindicated by a curve 101 of a graph of a pressure value and a positionin the x axis direction shown in FIG. 9 (a graph in an upper part ofFIG. 9).

A distribution of pressure values in the pressure detecting unit 42-2 inthe statically determinate state also has a substantially symmetricalcurved shape with the pressure value in the pressure center position D(around the graduation 9) set as the maximum and pressure values at bothends of a distribution range of the pressure values set as the minimumas indicated by a curve 102 of the graph of a pressure value and aposition in the x axis direction shown in FIG. 9 (the graph in the upperpart of FIG. 9).

The pressure value detected by the pressure detecting unit 42-1 islarger than the pressure value detected by the pressure detecting unit42-2 because, whereas the pressure detecting unit 42-1 is substantiallydirectly pushed by the pressure tip A, pressure by the pressure tip A isindirectly transmitted to the pressure detecting unit 42-2 via thedeforming section 41. Times until the pressure values come into thestatically determinate state are different because of a difference inpressure propagation speed depending on whether the pressure istransmitted via the deforming section 41.

When there is no viscoelasticity below or above the pressure detectingunit 42, the pressure detecting unit 42 comes into a state ofsubstantial point-contact with the tip A and only a pressure value ofthe sensor element 52 located in the pressure center position C or thepressure center position D is detected. Therefore, the pressuredistribution of the graph of a pressure value and a position in the xaxis direction shown in FIG. 9 is not generated.

In this way, the deforming section 41 is deformed according to a loadand a pressure value corresponding to the deformation is detected by thepressure detecting unit 42. Since the deforming section 41 made of aviscoelastic body is provided below or above the pressure detecting unit42, a pressure distribution equal to or larger than a contact area of acontact object (the pressure tip A) is generated. Therefore, thepressure distribution is in a wide range and noise in a pressure centercalculation result is reduced.

FIG. 10 shows an example of a shape of the input section 31 beforeshifting (on an upper side of the figure) and an example of a shape ofthe input section 31 after shifting (on a lower side of the figure). Astate of the input section 31 before shifting shown in FIG. 10represents a state same as the state of the input section 31 afterloading shown in FIG. 8 (on the lower side of FIG. 8).

In FIG. 10, as indicated by the state before shifting, the load Fz inthe minus direction (the downward direction in the figure) of the z axisis applied to the input section 31 by the depression of the inputsection 31 by the pressure tip A. Then, as indicated by the state aftershifting, while the pressure tip A keeps on depressing the input section31, a shifting operation for shifting the pressure tip A in the minusdirection (the right direction in the figure) of the x axis is performedby a shearing force Fs. In the example in FIG. 10, a position of thepressure tip A is fixed and the entire sensor 21 moves in the leftdirection in the figure while maintaining positions on the y axis andthe z axis, whereby the shifting operation is performed.

The input section 31 is shear-deformed by the shifting operation in theminus direction of the x axis while keeping the binding surface with thefixing section 32 fastened. As a result, a pressure distributionpositional relation with respect to the sensor elements 52 located inthe pressure center positions C and D by the load Fz before shifting ischanged.

Pressure distributions before shifting and after shifting are shown inFIG. 11. The pressure distribution before shifting (on an upper side ofthe figure) has a substantially symmetrical curved shape with thepressure values in the pressure center positions C and D set as themaximum and pressure values at both ends of a distribution range ofpressure values set as the minimum. However, in a pressure distributionafter shifting (on a lower side of the figure), a distribution range ofpressure values is narrower than that before shifting. Moreover, thepressure center positions C and D before shifting are in positionsslightly shifted in the minus direction of the x axis. The pressuredistribution has a shape gently curved more in the minus direction ofthe x axis than in the plus direction of the x axis.

A curve 111 in FIG. 11 indicates a pressure distribution before shiftingdetected by the pressure detecting unit 42-1, a curve 112 indicates apressure distribution before shifting detected by the pressure detectingunit 42-2, a curve 113 indicates a pressure distribution after shiftingdetected by the pressure detecting unit 42-1, and a curve 114 indicatesa pressure distribution after shifting detected by the pressuredetecting unit 42-2.

In this way, an amount of deformation of the pressure distributionincreases depending on a magnitude of the shearing force Fs. Therefore,even if a contact area between the viscoelastic body of the inputsection 31 (the deforming section 41) and the contact object (thepressure tip A) is generally unchanged, a “slip” in a broad sense can begrasped. Therefore, when gripping is performed by the robot hand 1, itcan be said that this is more effective to detect a slip in a state of“shift” and perform gripping force control than performing grippingforce control on the basis of a complete relative motion between theviscoelastic body of the input section 31 and the contact object.

Subsequently, attention is paid to a change in pressure center positionsof the pressure detecting unit 42-1 and the pressure detecting unit 42-2due to the shifting operation.

As shown in FIG. 8, when the load Fz in the minus direction of the zaxis is applied to the input section 31, the deforming section 41 isdeformed. However, the pressure center position C of the pressuredetecting unit 42-1 and the pressure center position D of the pressuredetecting unit 42-2 are in the same position around the graduation 9.

However, when the shifting operation in the minus direction of the xaxis is performed by the shearing force Fs (i.e., the entire sensor 21is moved in the left direction in the figure while positions on the yaxis and the z axis are maintained) as shown in FIG. 10, the pressurecenter position C of the pressure detecting unit 42-1 changes to about agraduation 6 and the pressure center position D of the pressuredetecting unit 42-2 changes to about a graduation 5.8. A difference ofabout 0.2 (hereinafter referred to as distance d) occurs between boththe pressure center positions.

This difference is also evident from the fact that, although positionsof cross marks (+) indicating positions of pressure centers on the curve111 and the curve 112 on the upper side of FIG. 11 coincide with eachother, positions of cross marks (+) indicating positions of pressurecenters on the curve 113 and the curve 114 on the lower side of FIG. 11shift from each other. In FIG. 12, the pressure center position C of thepressure detecting unit 42-1, the pressure center position D of thepressure detecting unit 42-2, and a shearing force at the time when thisshifting operation is performed are shown according to the elapse oftime. The difference described above is also evident from the fact thatthere is a difference between the pressure center position C (a curve121) of the pressure detecting unit 42-1 and the pressure centerposition D (a curve 122) of the pressure detecting unit 42-2 at the timewhen the shearing force (a curve 123) is substantially fixed.

FIG. 13 is a diagram showing the states in FIG. 10 as models of a pureshearing stress state. Dotted lines surrounding the pressure centerposition C of the pressure detecting unit 42-1 and the pressure centerposition D of the pressure detecting unit 42-2 schematically indicatecontour lines of pressure.

A model on an upper side of the figure indicates that, as describedabove, the pressure center position C of the pressure detecting unit42-1 and the pressure center position D of the pressure detecting unit42-2 are in a relation in which the pressure center positions coincidewith each other on a sensor matrix (an XY plane) in a state in which theshearing force Fs does not act.

A model on a lower side of the figure indicates that, when the shearingforce Fs (a shearing stress σ) is further applied in the minus directionof the x axis, in a state in which a slip against the pressure tip Adoes not occur on the surface of the sensor 21, as described above, adifference occurs on the sensor matrix between the pressure centerposition C of the pressure detecting unit 42-1 in the upper layer andthe pressure center position D of the pressure detecting unit 42-2 inthe lower layer.

According to these models, when a modulus of rigidity of a material isrepresented as G and the thickness of the deforming section 41 isrepresented as t, t×tan θ is the distance d and the shearing stress σ isrepresented by formula (15). When a shearing stress in the y axisdirection is generated, the same shift amount is generated on the plane.σ=G×t×tan θ  (15)

Therefore, at this point, a position corresponding to the pressurecenter position C of the pressure detecting unit 42-1 on the sensormatrix (the XY plane) of the pressure detecting unit 42-2 is set in aposition corresponding to the pressure center position C of the pressuredetecting unit 42-1 on the sensor matrix of the pressure detecting unit42-2 before the shifting operation (i.e., in the case of these models, aposition same as the pressure center position D of the pressuredetecting unit 42-2 before the shifting operation). The pressure centerposition D of the pressure detecting unit 42-2 after the shiftingoperation is set in a pressure center position calculated from adistributed pressure value detected after the shifting operation by thepressure detecting unit 42-2. Then, the main control unit 101 cancalculate “t×tan θ” on the basis of information on those positions.Therefore, the shearing stress σ can be calculated from formula (15).

In other words, according to this embodiment, a slip in a broad sensecan be detected according to a pressure distribution generated becausethe deforming section 41 is a viscoelastic body. A shearing stress atthat point can be detected. Therefore, it is possible to accuratelyacquire information on a slip necessary for stable gripping, skillfulmanipulation, and the like of an object by a robot hand.

In the above explanation, a slip is regarded as being detected when theslip sense detection value calculated by the formula (9) exceeds thethreshold for judgment. However, it is also possible to regard a slip asbeing detected when a difference (the distance d) between the pressurecenter position C of the pressure detecting unit 42-1 and the pressurecenter position D of the pressure detecting unit 42-2 reaches an amountequal to or larger than a fixed amount or when the distance d reaches anamount equal to or larger than the fixed amount at speed equal to orhigher than fixed speed.

Further, for example, it is also possible to calculate a difference ofstress propagation speed from the time difference until the staticallydeterminate state obtained from the transition of the pressure centerposition C of the pressure detecting unit 42-1 and the pressure centerposition D of the pressure detecting unit 42-2 shown in FIG. 12 and usethe difference for slip detection.

In other words, it is possible to more accurately detect a slip in abroad sense.

FIG. 14 shows an example of the external structure of the sensor 21shown in FIG. 2. In the example in FIG. 14, plan views of sensors 201 to204 having different shapes of the input section 31 viewed from rightabove are shown in an upper part of the figure. Sectional views of thesensors 201 to 204 are shown in a lower part of the figure.

The sensor 201 includes the input section 31 of a columnar shape inwhich an input surface 31 a is circular viewed from right above and issquare viewed from a side. The sensor 202 includes the input section 31of a dome shape in which the input surface 31 a is circular viewed fromright above and is dome-shaped viewed from a side. The sensor 203includes the input section 31 of a semicylindrical shape in which theinput surface 31 a is square viewed from right above and issemicylindrical-shaped viewed from a side.

The sensor 204 includes the input section 31 of a columnar shape inwhich the input surface 31 a is doughnut-shaped viewed from right aboveand is square-shaped viewed from a side with the input section 31 formedabove and below the fixing section 32 to hold the fixing section 32. Ina hole (hollow) section of a doughnut in the sensor 204, a shaft can beprovided as indicated by a dotted line.

As in the sensor 201 and the sensor 202 described above, a shape of theinput section 31 can also be formed to form the input surface 31 acircular.

A shape of the input section 31 viewed from the side can also be a domeshape and a semicylindrical shape like the sensor 202 and the sensor203. The dome shape and the semicylindrical shape of the sensor 202, thesensor 203, and the like are suitable when the sensors come into contactwith an object, for example, when the sensors are provided in the robothand 1 because an error of detection easily caused when a plane objectis brought into contact with the sensors in a plane can be controlled.

Moreover, a shape of the input section 31 can also be a doughnut shapelike the sensor 204. In this case, since a shaft can be inserted througha doughnut portion, for example, the input section 31 is suitable forbeing provided in respective joint sections of the robot hand 1 and thelike.

FIG. 15 shows another example of the material of the input section 31shown in FIG. 2. In the example in FIG. 15, a side sectional view of asensor 211 added with an electrostatic shield for preventing leakage andintrusion of static electricity is shown.

The sensor 211 is different from the sensors described above in that thefixing section 32 is replaced with a fixing section 233 having a shieldfunction, the pressure detecting unit 42 is integrated with aviscoelastic body 231 having a shield function of the deforming section41, and thin-film silicon rubber 232 is integrally formed on a surfaceof the pressure detecting unit 42 by, for example, a two-color moldingmethod.

The pressure detecting unit 42 is shielded from the viscoelastic body231 above and the fixing section 233 below the pressure detecting unit42. Consequently, it is possible to further control the fall inperformance of the pressure detecting unit 42.

As explained above, the sensor 21 is configured in a multilayerstructure in which the capacitance-type pressure sensor that detects anormal force perpendicular to the sensor surface (the input surface 31a) and the viscoelastic material are combined. Signal processing for,for example, calculating a pressure center position is performed byusing a pressure value from the sensor 21. Therefore, it is possible tomore surely detect a slip of an object by a tangential force orthogonalto the normal force and a direction of the slip. Since the sensor 21includes the pressure detecting unit 42 in the two layers, it ispossible to more accurately calculate a shearing force and improveaccuracy of slip detection.

The slip includes not only a “rolling motion” of a complete “relativemotion” and a complete “rotational motion” between fingers and an objectbut also an “initial local slip” and “shift”.

Therefore, in the robot hand manipulator shown in FIG. 1 to which thesensor 21 is applied, since the “slip” including the complete “relativemotion”, the “initial local slip”, and the “shift” between the fingersand the object can be detected, it is possible to more surely detect the“slip” than the detection of only a slip in a narrow sense representedby a stick slip phenomenon. Consequently, it is possible to prevent afall and the like of an object and accurately grip and manipulate (moveor carry) an arbitrary object.

Moreover, since the sensor 21 is made of a flexible material, safety forhumans is improved and it is possible to realize physical interactionwith higher affinity with humans.

It is also possible to apply the sensor 21 to various input devices(e.g., a remote controller) with high affinity with humans for input toa real world machine and a virtual space by using a flexible materialwith high affinity with humans and having softness and slippingproperties in the input unit. For example, it is possible to represent aforce and pressure but also slip phenomena such as “shift of a materialitself”. Therefore, it is conceivable to realize a new-sense humaninterface having a wider variety of representation input means.

In a robot hand and a manipulator, to skillfully grip and manipulatearbitrary objects having various sizes, shapes, surface states, andweights and perform physical interaction with high affinity with humans,it is necessary that dynamic behaviors of an object such as slipsrepresented by “translation”, “rolling”, and “shift” and “oscillation”observed at the time of an initial local slip can be detected inaddition to “a magnitude, a direction, and a distribution of a force”.Moreover, in portions corresponding to fingertips and skins that grip anobject, softness (viscoelasticity, super elasticity, and rubber-likefeature) optimum for gripping and grippability by friction of a surfaceare necessary.

On the other hand, in machines (a remote controller, a controller, aswitch, etc.) manually operated by humans, in general, a sensor devicethat accurately detects a finger-tip generated force and a position ofthe force is necessary. If even movement, a slip, and the like offingertips can be used as input information, the sensor device can be anew-sense user interface. If places to which the fingertips come intocontact are made soft to improve affinity with humans, this also leadsto a new-sense user interface.

As described above, the sensor 21 according to this embodiment isconfigured by a combination of the viscoelastic body and thecapacitance-type pressure sensor. Therefore, for example, viscoelasticbodies attached to surfaces of a robot hand and a manipulator and,moreover, an entire robot and having softness like the human skin arechanged to various shapes by a force received from the outside and aform of the force. Consequently, when an object comes into contact withthe sensors 21, pressure is dispersed to capacitance-type pressuresensors. Consequently, it is possible to calculate a pressure center ina robust manner.

By using this pressure center for sensing of a slip sense of skins ofthe surfaces of the robot hand and the manipulator and the entire robot,amounts equivalent to a slip direction and slip speed can be acquired bythe slip sense. Therefore, it is possible to perform control of objectgripping and manipulation control for treating an object while slippingthe object with fingertips of the robot hand.

As described above, with the sensor according to this embodiment, thereis an effect that it is possible to easily perform accurate gripping andmanipulation of an arbitrary object in the robot hand manipulator andthere is also an effect that prevention of a fall (slip fall) of anobject and safety for humans are realized by contact detection and slipdetection. Moreover, because of the soft material, it is possible toeasily realize physical interaction with high affinity with humans.

In the above explanation, the pressure detecting unit 42 detects adistributed pressure value using a capacitance change as a detectionprinciple. However, the pressure detecting unit 42 can also beconfigured to detect a distributed pressure value using not only thecapacitance change but also, for example, a resistance change as adetection principle. If a distributed pressure value can be obtained, asensor configured by simply arranging pressure sensitive rubber may beused.

In the above explanation, the sensors 21 are provided in the arm, thehand, and the like of the robot hand manipulator. However, the presentinvention can also be applied to fields, products, and the like such asjoint mechanism sections of various robots, controllers and joy sticksfor games, various input devices, shock absorbing devices, biometricdevices, health care products, and sports fields.

It is possible to cause hardware to execute the series of processing orcause software to execute the series of processing.

In causing the software to execute the series of processing, a programconfiguring the software is installed, from a program recording medium,in a computer incorporated in dedicated hardware or a general-purposepersonal computer or the like that can execute various functions byinstalling various programs.

FIG. 16 is a block diagram showing an example of the structure of apersonal computer 301 that executes the series of processing accordingto a program. A CPU (Central Processing Unit) 311 executes various kindsof processing according to programs stored in a ROM (Read Only Memory)312 or a storing unit 318. Programs executed by the CPU 311, data, andthe like are stored in a RAM (Random Access Memory) 313 as appropriate.The CPU 311, the ROM 312, and the RAM 313 are connected to one anothervia a bus 314.

An input/output interface 315 is also connected to the CPU 311 via thebus 314. The sensors 21, an input unit 316 including a keyboard, amouse, and a microphone, and an output unit 317 including a display anda speaker are connected to the input/output interface 315. The CPU 311executes various kinds of processing in response to commands inputtedfrom the input unit 316. The CPU 311 outputs a result of the processingto the output unit 317.

The storing unit 318 connected to the input/output interface 315includes, for example, a hard disk and stores programs executed by theCPU 311 and various data. A communication unit 319 communicates withexternal apparatuses via networks such as the Internet and a local areanetwork.

A program may be acquired via the communication unit 319 and stored inthe storing unit 318.

A drive 320 connected to the input/output interface 315 drives, when aremovable medium 321 such as a magnetic disk, an optical disk, amagneto-optical disk, or a semiconductor memory is inserted, theremovable medium 321 and acquires programs, data, and the like recordedon the removable medium 321. The acquired programs and data aretransferred to the storing unit 318 and stored when necessary.

A program recording medium that stores programs installed in a computerand executable by the computer includes the removable medium 321 as apackage medium including a magnetic disk (including a flexible disk), anoptical disk (including a CD-ROM (Compact Disc-Read Only Memory) and aDVD (Digital Versatile Disc)), a magneto-optical disk, or asemiconductor memory, the ROM 312 in which programs are temporarily orpermanently stored, and the hard disk configuring the storing unit 318.The storage of the programs in the program recording medium is performedby using a wired or wireless communication medium such as a local areanetwork, the Internet, or a digital satellite broadcast via thecommunication unit 319 as an interface such as a router or a modem whennecessary.

In this specification, steps that describe the programs stored in theprogram recording medium include not only processing performed in timeseries according to a described order but also processing executed inparallel or individually, although not always executed in time series.

Embodiments of the present invention are not limited to the embodimentdescribed above. Various modifications of the embodiment are possiblewithout departing from the spirit of the present invention.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations, and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A detecting device including a pressure sensor that is deformed by aload from an outside and causes stress dispersion, the detecting devicecomprising: slip detecting means for calculating a pressure centerposition using a pressure value detected by the pressure sensor,calculating a movement value of the calculated pressure center positionusing a temporal change of the pressure center position, and detecting aslip on the basis of the calculated movement value of the pressurecenter position, wherein the pressure sensor has a multilayer structurein which two detecting units that detect pressure are arranged to hold aviscoelastic body made of a viscoelastic material that is deformed by aload from the outside, wherein the pressure value detected by thepressure sensor is a dispersed pressure value of an object gripped byfingertips of the viscoelastic body, the pressure value being detectedwhen the object comes into contact with the viscoelastic body, and thepressure sensor detects a slip between the gripped object and thefingertips of the viscoelastic body on the basis of the detecteddispersed pressure value.
 2. A detecting device according to claim 1,wherein the slip detecting means calculates a pressure center positionfrom a pressure distribution generated in the viscoelastic body bystress dispersion detected by a first one of the detecting units,calculates a pressure center position from a pressure distributiongenerated in the viscoelastic body by stress dispersion detected by asecond one of the detecting units, and calculate a difference betweenthe pressure center positions.
 3. A detecting device according to claim2, wherein the slip detecting means detects the slip on the basis of thecalculated difference.
 4. A detecting device according to claim 2,wherein the slip detecting means detects, on the basis of the calculateddifference, a shearing force applied to the pressure sensor.
 5. Adetecting device according to claim 1, wherein the slip detecting meanscalculates, from a pressure distribution generated in the viscoelasticbody by stress dispersion detected by a first one of the detecting unitsand a pressure distribution generated in the viscoelastic body by stressdispersion detected by a second one of the detecting units, a differencebetween propagation speed of pressure detected by the first detectingunit and propagation speed of pressure detected by the second detectingunit.
 6. A detecting device according to claim 5, wherein the slipdetecting means detects the slip on the basis of the calculateddifference.
 7. A detecting device according to claim 1, wherein the slipdetecting means judges whether a movement value of the calculatedpressure center position is equal to or larger than a predeterminedthreshold and, when it is judged that the movement value of the pressurecenter position is equal to or larger than the predetermined threshold,detects the slip.
 8. A detecting device according to claim 1, whereinthe slip detecting means judges whether a sum of movement values of thecalculated pressure center position is equal to or larger than apredetermined threshold and, when it is judged that the sum of themovement values of the pressure center position is equal to or largerthan the predetermined threshold, detects the slip.
 9. A detectingdevice according to claim 8, wherein the slip detecting means multipliesthe movement values of the calculated pressure center position withcoefficients corresponding to levels of the movement values of thepressure center position to calculate a sum of the movement values ofthe pressure center position.
 10. A detecting device according to claim1, wherein the slip detecting means calculates a difference of amovement average value of the calculated pressure center position tocalculate a movement value of the pressure center position.
 11. Adetecting device according to claim 1 wherein the slip detecting meanscalculates a difference of the calculated pressure center position tocalculate a movement value of the pressure center position.
 12. Adetecting device according to claim 1, wherein the pressure sensorincludes plural elements, and the slip detecting means detects, using apressure value detected by the pressure sensor, an element that performsdetection of contact of an object with the pressure sensor andcalculates a movement value of the pressure center position using apressure value from the detected element.
 13. A detecting deviceaccording to claim 1, wherein the pressure sensor has a viscoelasticbody made of a viscoelastic material on a surface thereof.
 14. Adetecting device according to claim 13, wherein the viscoelastic body isintegrated with thin-film silicon rubber by a two-color molding method.15. A detecting device according to claim 13, wherein the viscoelasticbody is molded with an electrostatic shield material mixed therein. 16.A detecting device according to claim 15, wherein the viscoelastic bodyand the pressure sensor are integrated with thin-film silicon rubber bya two-color molding method.
 17. A detecting device including a pressuresensor that is deformed by a load from an outside and causes stressdispersion, the detecting device comprising: a slip detecting unitcalculating a pressure center position using a pressure value detectedby the pressure sensor, calculating a movement value of the calculatedpressure center position using a temporal change of the pressure centerposition, and detecting a slip on the basis of the calculated movementvalue of the pressure center position, wherein the pressure sensor has amultilayer structure in which two detecting units that detect pressureare arranged to hold a viscoelastic body made of a viscoelastic materialthat is deformed by a load from the outside, wherein the pressure valuedetected by the pressure sensor is a dispersed pressure value of anobject gripped by fingertips of the viscoelastic body, the pressurevalue being detected when the object comes into contact with theviscoelastic body, and the pressure sensor detects a slip between thegripped object and the fingertips of the viscoelastic body on the basisof the detected dispersed pressure value.
 18. A robot apparatuscomprising: a pressure sensor that is deformed by a load from an outsideand causes stress dispersion, a slip detecting unit calculating apressure center position using a pressure value detected by the pressuresensor, calculating a movement value of the calculated pressure centerposition using a temporal change of the pressure center position, anddetecting a slip on the basis of the calculated movement value of thepressure center position, and a control unit controlling a movement ofthe robot apparatus according to the slip detected by the slip detectingunit, wherein the pressure sensor has a multilayer structure in whichtwo detecting units that detect pressure are arranged to hold aviscoelastic body made of a viscoelastic material that is deformed by aload from the outside, wherein the pressure value detected by thepressure sensor is a dispersed pressure value of an object gripped byfingertips of the viscoelastic body, the pressure value being detectedwhen the object comes into contact with the viscoelastic body, and thepressure sensor detects a slip between the gripped object and thefingertips of the viscoelastic body on the basis of the detecteddispersed pressure value.
 19. An input device comprising: a pressuresensor that is deformed by a load from an outside and causes stressdispersion, a slip detecting unit calculating a pressure center positionusing a pressure value detected by the pressure sensor, calculating amovement value of the calculated pressure center position using atemporal change of the pressure center position, and detecting a slip onthe basis of the calculated movement value of the pressure centerposition, wherein the pressure sensor has a multilayer structure inwhich two detecting units that detect pressure are arranged to hold aviscoelastic body made of a viscoelastic material that is deformed by aload from the outside, wherein the pressure value detected by thepressure sensor is a dispersed pressure value of an object gripped byfingertips of the viscoelastic body, the pressure value being detectedwhen the object comes into contact with the viscoelastic body, and thepressure sensor detects a slip between the gripped object and thefingertips of the viscoelastic body on the basis of the detecteddispersed pressure value.